Etherified amino formaldehyde products



July 9, 1968 H. P. A. GROLL 3,392,150

ETHERIFIED AMINO FORMALDEHYDE PRODUCTS Original Filed Aug. 5, 1963INVENTOR HERBERT P. A. GROLL igaj Spill? AT TOR N EYS.

United States Patent 3,392,150 ETHERIFIED AMINO FORMALDEHYDE PRGDUCTSHerbert P. A. Groll, Pixbo, Sweden Continuation of application Ser. No.299,893, Aug. 5, 1963, which is a continuation-in-part of applicationSer. No. 43,916, July 19, 1960. This application Jan. 5, 1967, Ser. No.607,577 Claims priority, application Great Britain, July 23, 1959,25,353/ 59 14 Claims. (Cl. 26067.6)

ABSTRACT OF THE DISCLOSURE Etherified amino formaldehyde resinscharacterized by fast curing good pot life, and which yield protectivefilms of good hardness, are produced by a continuous process. Theprocess includes a first step in which an amino-formaldehydecondensation product is produced from, for example, urea andformaldehyde; a second step in which the said condensation product isdehydrated by rapid heating to produce a substantially anhydrous,unstable melt, and a third step in which the said condensation productis etherified with an alcohol. Overall time for the three steps can beless than one hour.

This application is a continuation-in-part of application Ser. No.43,916, filed July 19, 1960, and is a continuation of application Ser.No. 299,893, filed Aug. 5, 1963.

This invention relates to an improved method for production ofetherified amino-formaldehyde resins as well as to improved resinsproduced by this method. As raw materials for these resins formaldehyde,an amido compound of carbonic acid, and a lower aliphatic alcohol withpreferably 4 or 5 carbon atoms are used. The term amido compounds ofcarbonic acid comprises those compounds containing NH -groups which uponcomplete hydrolysis yield carbonic acid and ammonia, e.g. urea,thiourea, and melamine. Examples of alcohols suitable for carrying outthis invention comprise e.g. normal and secondary butyl alcohol,iso-butyl alcohol, normal amylalcohol and the iso-amyl-alcohols.

The reaction products, etherified amino-formaldehyde resins, arecommercially produced with a great variety of properties and usedchiefly as constituents in surface coating compositions, especially incombination with alkyd resins and epoxy resins.

The reactions leading from the raw materials enumerated to the productsmentioned consist in the first iristance of an addition of at least onemolecule of formaldehyde to every NH -group of the amido compoundwhereby a methylol compound is formed. This methylol compound is thensimultaneously etherified with one of the alcohols enumerated above andcondensed to an increased molecular weight whereby the product, usuallyobtained as solution in an excess of the alcohol used, becomes viscousto the degree desired for its use as a constituent in surface coatingcompositions.

3,392,150 Patented July 9, 1968 While it is recognized that it isdesirable to remove the water, introduced into the reaction mixture bythe aqueous formaldehyde, from the methylol compound completely beforereacting the methylol compound with the alcohol chosen, this manner ofoperation has met in practice with difficulties because of the highmelting point of the methylol compound and of the fact that the methylolcompound decomposes rapidly at its melting point. Therefore, the commonpractice in the prior art was to dehydrate the methylol compound only tosuch a degree that the resulting reaction mixture is still liquid at C.at which temperature the compound is sufficiently stable to be handledin commercial batches. This means in the case of dimethylol urea that atleast 15% of water must remain in the reaction mixture. In the case ofmelamine formaldehyde condensation products practically no water couldbe removed before the alcohol was added, so that all the water of theaqueous formaldehyde together with the Water formed during theetherification and condensation had to be removed as an azeotrope withthe alcohol. This is a decided disadvantage of the older processes notonly because the azeotropic distillation is a time consuming operation,but also because the lengthy treatment of the reaction product underthese conditions has an unfavorable influence on the quality of theproduct obtained.

It has therefore been suggested to produce methylol compounds of urea,containing so much combined formaldehyde that the addition compound byprolonged heating at 6090 C. in aqueous solution looses itscrystallizability and in practically anhydrous condition is a syrupyliquid with such a low melting point that it is quite stable even attemperatures considerably above its melting point. However, if thesesyrupy polymethylol compounds of urea are etherified with one of thealcohols mentioned, the resulting resins have inferior curing propertiesand produce soft coating films With inferior gloss. If the ratio offormaldehyde to urea in these methylol compounds exceeds about 2.7,additional urea must be added during the etherification and condensationstep. This is an undesirable complication of the operating technique,and most of the time saved by avoiding the azeotropic distillation islost again by this additional operation.

It has now been found that all the above-mentioned difficulties can beovercome if the reaction compound of formaldehyde and the amino compoundchosen is dehydrated according to copending application Ser. No.565,256, filed Feb. 13, 1956 (replaced by Ser. No. 254,547, filed I an.14, 1963) and the corresponding British Patent 801,404, and the highlyunstable fused product instead of being allowed to solidify to form astable solid, is reacted directly with the hot acidified alcohol chosen.The dehydrated fused dimethylol urea obtained according to this patentcan contain only 25% of water, while the dehydrated fused methylolmelamine can contain only 7% of Water.

The melting points of the preferred melts used according to thisinvention were found to be above C. At the relatively high transfertemperatures necessitated by their melting points the life of the meltswhich are to be reacted with the hot acidified alcohol, is quitelimited.

Thus, a melt of the reaction product of 2.5 mols of formaldehyde per 1mol of urea containing 3% of water solidified at 65 C. to a crystallinesolid which had a melting point of 120 C. This melt was withdrawn fromthe evaporator into a test tube at 95 C. and maintained at 110 C. byinserting the test tube into a hot oil bath. After /2 minutes anamorphous precipitate began to appear and after 13 minutes the wholemass had turned to an insoluble and infusible solid. A melt of thereaction product of 2.2 moles of formaldehyde with 1 mol of ureacontaining 3% of water crystallized at 75 C. and showed a melting pointof about 120 C. The melt was withdrawn from the evaporator into a testtube at 100 C. and when it was maintained at 110 C. it became cloudyafter 5 minutes and turned into an insoluble, infusible solid after 8minutes.

When as much as 2.7 mols of formaldehyde was used per mol of urea thedehydrated melt containing 3.3% of water did become pasty and finallysolid only after 45 minutes at room temperature. However, the meltingpoint of the solid was 105 C. This melt drawn from the evaporator in themanner described above had at 110 C. a life time of 14 minutes andbecame solid after 25 minutes. This amorphous solid was insoluble inwater and in butanol and completely unreactive with acidified alcohols.An attempt to melt it resulted in heavy decomposition with liberation ofgaseous formaldehyde.

Even a melt produced by dehydrating the reaction product of 3.0 mols offormaldehyde with 1 mol of urea eventually did solidify after a fewhours at 25 C. This microcrystalline solid had a melting point of 97 C.However, the melt from the evaporator when kept at 110 C. became cloudyafter 14 minutes and solid after 25 minutes. This amorphous solid wasinsoluble in water, butanol and all other organic solvents tried and hadcompletely lost its reactivity with acidified alcohols.

A melt of the reaction product of 4.5 mols formaldehyde per 1 molmelamine containing about 7% water had a solidification temperature of108 C. This solid, though crystalline, could, however, only partly beremelted at about 125 C. with decomposition and formation of aninfusible white crust. The easily mobile melt drained from theevaporator into a test tube, maintained at 110 C. became cloudy after6090 seconds and thereafter rapidly turned viscous and lost its abilityto react with acidified butanol. It had become completely unreactiveafter minutes and gradually became solid within 15 to minutes from thestart of the experiment. Thus, in each of the cases described above thesolid degeneration products were insoluble, unreactive and infusibleand, hence, useless for producing coating resins.

In the process of the invention, difiiculty due to the short life of themelt is avoided by continuously and rapidly transferring the melt fromthe evaporator to the mixing chamber in which the melt is contacted withthe acidified alcohol. In a pilot plant according to the flow sheet ofthis application, which is described in detail hereinafter, the time fortransfer from the evaporator to the mixing reactor was usually secondsfor products with comparatively long life. For products with shorterlife, the transfer time was reduced to 15 seconds. For a full sizeplant, more favorable pipe dimensions can be chosen and the transfertime can be reduced to about 5 seconds. For melts with extremely shortlife, it has been found useful to emulsify the melt with some of thealcohol without addition of acid catalyst, prior to entry of thematerial into the transfer pump, or to effect the emulsification in thetransfer pump. By this procedure clogging of the pump due tosolidification of films between moving parts can be avoided. Thisprocedure does not, however, lengthen the life of the melt, and,accordingly, when this procedure is used, the transfer should beeffected rapidly.

It must be emphasized that in the process of the invention the advantageof using high temperatures of evaporation and transfer resides not onlyin the fact that solidification is avoided but to a much higher degreein the expediency of extremely fast evaporation and fast reaction ofetherification. By the combination of the three factors, extremely shortand effective evaporation of the water from the melt, short transfertime, and fast etherification of the methylol product with the acidifiedalcohol, as will be described below, the structure of the resin has notime to degenerate. The practical result of this novel combination offeatures leads to superior curing characteristics of the resinsobtained.

Thus, the invention provides a process for the etherification ofwater-soluble, substantially anhydrous condensation products offormaldehyde and an amino compound containing the group in which X is amember selected from the group consisting of I O, S, and N(|3 Theprocess comprises continuous passing the condensation product in moltenform in contact with an alcohol in liquid form. The alcohol is of thegroup primary and secondary monohydric and polyhydric aliphaticalcohols. An acid catalyst is included in the reaction medium. Thecontacting is carried out in a flow path at a temperature above about C.and for a residence time of less than 1 hour, the conditions being suchthat etherification of the condensation product is effected by thealcohol. The contacting in a flow path can be in any suitable mannerwherein the materials are brought together for reaction and thetime-temperature conditions are such that undesirable reactions do notoccur. Thus, the process of the invention is particularly well suited tocontinuous operation of the process, as, for example, by effecting thecontacting along a continuous flow path into which the reactants arecontinuously introduced and from which product is continuouslywithdrawn.

Best results are obtained when the water-soluble, substantiallyanhydrous condensation product of formaldehyde and an amino compound ofthe formula set forth above is produced by the method of copendingapplication Ser. No. 565,256, filed Feb. 13, 1956. Thus, the aminocompound and formaldehyde are condensed in an aqueous medium to form acondensation product in aqueous solution, and the medium containing suchproduct is then rapidly heated to expel water therefrom and provide asubstantially anhydrous melt of the condensation product. Thissubstantially anhydrous condensation product can contain water to theextent disclosed in the said copending application. Thus, thecondensation product is substantially anhydrous and by this, is meantthat it contains not more than about 15% by weight of water. In the caseof urea formaldehyde condensation product, the water content can be 23%;in the case of melamine formaldehyde, the water content can 'be about 7%or lower than about 7%. The substantially anhydrous melt ischaracterized in that it is soluble in water with unlimited dilution,i.e. the melt of the condensation product is a hydrophilic melt. Thismelt is particularly well suited for contacting, as is described above,with an alcohol for the etherification of the melt to form the productswhich the invention provides. Preferably the melt is crystallizable oncooling. The crystallizability is enhanced by avoiding prolonged heatingof the aqueous reaction mixture between formaldehyde and the amidocompound of carbonic acid.

As noted above, it has been proposed in the prior art to employ foretherification as is the concern of the invention, methylolaminecompounds wherein the ratio of methylol groups to amino groups, on thebasis of the use of urea, is in excess of about 2.5 methylol groups perurea molecule and the aqueous reaction mixtures is heated for such alength of time that it will leave a syrupy residue on evaporation of thewater. The resort to such operating conditions occasions disadvantages.In the procedure of the invention, such a high ratio of methylol groupsto amino groups is preferably not employed. Thus, in the preferredembodiment of the invention, the ratio of methylol groups to aminogroups, based on urea, is less than about 2.5 methylol groups per ureamolecule. This ratio of methylol to amino groups is preferably in therange of 2.0-2.5 and very good results are obtained when the ratio is2.5. In the case of melamine, the ratio can be considerably higher. Withmelamine a ratio of 1 mol of melamine to 4.5 mols and even 6 mols offormaldehyde provides good results. As noted above, the condensationproduct of formaldehyde and an amino compound can be produced by themethod of the said copending application. The disclosure of the saidcopending application and the disclosure of the continuation-in-partthereof, Ser. No. 254,547, filed Jan. 24, 1963, are incorporated hereinby reference. In the evaporation of water to provide the substantiallyanhydrous melt, the pH is maintained above about 6.5, and is preferablymaintained above about 8.

The alcohols which can be used for the etherification are primary andsecondary monohydric and polyhydric aliphatic alcohols. Preferably,these alcohols have up to about 8 carbon atoms. Highly successfulresults have been obtained with alcohols containing 45 carbon atoms. Theetherification products produced with alcohols contained about 4-8carbon atoms are particularly desired according to the invention, sincethese products are soluble in the usual paint solvents along with othercoating composition ingredients. Thus, these resins are soluble inorganic solvents. The etherification products produced with alcoholscontaining up to 3 carbon atoms are desirable in that these products,such as the etherification product formed with methanol, the productformed with ethanol, or the product formed with isopropanol, arewater-soluble and hence, can be used in coating compositions employingan aqueous vehicle. Glycols, for example ethylene glycol, can be used,and provide water-soluble amino resins.

As has been indicated above, it is important in the practice of theinvention to rapidly transfer the melt of the amino-formaldehydecondensation product to a reaction zone wherein etherification iseffected. Thus, in the process of the invention, the substantiallyanhydrous melt can be formed in an evaporating zone, and this melt canbe removed from the evaporating zone immediately following its formationand transferred to the flow path for contacting with the alcohol. Thetransfer should be made in a period of less than about 2 minutes. Therapidity with which the transfer must be made depends on the ratio ofmethylol to formaldehyde groups, and the lower this ratio, the morerapid should be the transfer. Thus, the transfer time can be about 2minutes where the ratio is 2.5 methylol groups per urea molecule; about60 seconds where this ratio is about 2.2; and about 30 seconds if theamino compound is melamine. A preferred transfer time is less than about15 seconds. The ultimate criterion, of course, for the transfer time isthat the transfer should be eifected sufiiciently rapidly so that noundesirable reaction of the amino-formaldehyde condensation productoccurs.

The time-temperature relationship for the etherification reaction issuch that the etherification occurs rapidly without the occurrence ofundesirable side reactions. The temperature can be in the range of about85l 75 C., or better in the range of l00175 C. The preerred temperaturerange is l10150 C. The reaction is a liquid phase reaction in that theamine-formaldehyde compound and the alcohol taking part in the reactionare in liquid phase. Desira'bly, an elevated pressure as is necessary tomaintain the reactants in liquid phase is employed. The etherificationproduct is completely soluble in the alcohol utilized for theetherification and a solution of this product in the alcohol isobtained. Prolonged contacting of the reactants is undesirable becausedetrimental side reactions may occur which cause the resin to becomesofter. It was found that the equilibrium between the simultaneouslyoccurring etherification of methylol groups with the alcohol,etherification between the methylol groups and, to a considerableextent, formation of CH -bridges, and their respective reversedreactions is reached rather rapidly.

In the etherification reaction, for the preferred range of -150 C., thetemperature is considerably above the boiling point of the azeotropicmixture at atmospheric pressure, and, for such operation,super-atmospheric pressure is used to prevent evaporation of theazeotrope from the hot reaction mixture.

As is stated above, the reaction time for the etherification, i.e. thesimultaneous etherification and condensation to a coating resin, is lessthan 1 hour. The preferred reaction time is between about 5 and 30minutes. The reaction times according to the invention are surprisinglyshort, particularly in view of the prior art practice wherein reactiontimes are between 1624 hours.

With respect to pH, in the reaction between formaldehyde and aminecompound, the medium is preferably weakly alkaline. The pH can be about8 or between about 8 and about 9. In the etherification step, the pH ismildly acid. The acid value can be between about 6 and about 7(expressed as milligrams of potassium-hydroxide consumed forneutralization of 1 gram of the mixture) for methylol melamines milderconditions are advantageously employed; the acid values can be about 1.

It has been found that secondary butyl alcohol can be usedsatisfactorily by applying this new method, provided that theconcentration of the acid catalyst was held be tween acid values of 2.5and 7.5 referably between 4 and 6. (The acid value is expressed asmilligrams KOH consumed for neutralizing 1 gram of a sample.) It wasfound that secondary alcohols will not react with the methylol compoundsat too low acid values so that the methylol compound itself willcondense to insoluble products instead of being etherified; at too highacid values the product will gelatinize. In contrast to this, whenprimary alcohols are etherified with dimethylolurea the acid value canbe varied within considerably wider limits.

If the low molecular, Water-soluble alcohols methanol and ethanol areused for etherification of a methylol melamine the reaction occursextremely rapidly and it was found necessary to interrupt the reactionafter a few minutes by neutralizing the acid catalyst. Otherwise a rapidpolymerisation will occur which would rapidly turn the product into auseless solid. From the neutralized reaction product the water ofreaction together with the unreacted excess of the alcohol can beremoved by evaporation with or without the use of an entraining agent.

The nature of the acid used is to a large extent immaterial for theresult obtained. Thus, hydrochloric acid, phosphorie acid, p-toluylsulphonic acid, formic acid, oxalic acid, phthalic acid, or mixtures oftwo or more of these acids, and even carbonic acid, formed byintroducing car- 'bon dioxide gas under pressure into the reactionmixture, all gave satisfactory results. Thus, obviously the hydrogen ionfunctions as catalyst. If organic acids are used as catalyst these areusually esterified with the alcohol during the dehydration step. Theresulting product has in this case a very low acid value. When formicacid is used, most of the ester formed distills off the product as anazeotropic mixture.

The short reaction times accommodate the process of this invention tocontinuous operation. When operating the process continuously, e.g. inan apparatus as described in the examples of this specification, it hasbeen found that the properties of the etherified amino resins produced,most important for their use as coating resins constituents,

i.e. the compatibility of the amino resins with various types of alkyds,the pigment wetting properties, the time required for curing the coatingfilm, and its hardness, can be adjusted most effectively by varying theoperating conditions in the etherification and condensation step. Oneoutstanding advantage of the method according to this invention, is thefact that it leads to etherified amidoformaldehyde resins which givesuperior curing properties and great hardness to the coating films inwhich they are used.

The variable which were found to influence the properties mentioned aretemperature and time of reaction of the fused, and therefore unstable,low molecular methylol amido compound with the acidified alcohol inpresence of the water formed by the reaction. If the time allowed forthis reaction is reduced, the finished dehydrated etherified resinsproduced need less and less time to cure and the resulting coating filmbecomes harder. However, the compatibility of the resin and its wettingproperties towards pigments becomes somewhat less favorable. If, on theother hand, the temperature of reaction is increased, the compatibility,the wetting properties and other film forming qualities are tremendouslyimproved.

When using urea and a primary alcohol such as normal butyl alcohol,iso-butanol, or the amyl-alcohols, surprisingly high reactiontemperatures up to 175 C. can be used. The preferred temperature whenusing the reagents mentioned, is around 150 C. while the time of thereaction may be varied between and 45 minutes according to thecompatibility of the resin, the rapidity of curing and the hardnessrequired. The fact that such high reaction temperatures are beneficialis quite surprising in view of the instability of the fused methylolcompound and still more so as said temperatures are even higher than theusual curing temperature of the etherified resin, i.e. the temperatureat which it rapidly turns to an insoluble solid.

When using secondary butyl alcohol it is advisable to carry out thetreatment at a lower temperature for example a maximum temperature of115 C. during a time of reaction of about 30 minutes. When usingmelamine and normal butyl alcohol, favorable results were obtained by atreatment between 110 and 115 C. during 15 minutes.

The reaction mixture which is the product of the etherification reactionchiefly contains, besides the partly etherified and partly condensedresin and the water of reaction, the excess of the alcohol used whichfunctions as solvent. In order to remove the water of reaction, the hotmixture is expanded into an evaporator from which the azeotrope of waterand the alcohol used is evaporated essentially at atmospheric orsubatmospheric pressure. Any flash evaporator or a thin film evaporatormay be used. In most cases the amount of water removed by azeotropicdistillation will deprive the resulting resin solution of so muchalcohol that the equilibrium composition of the resin will shift muchtoward condensation. To counteract this efiiect, an additional quantityof alcohol is introduced either as liquid into the stream of the hotreaction mixture to the evaporator or as vapor into the evaporator.

A further considerable improvement was achieved by carrying out thedehydration of the etherified reaction product in a column. By blowingdry vapor of the alcohol used for the etherification into the bottom ofthe continuously operating column in countercurrent to the expandedreaction mixture, a very efiicient dehydration of the resin solution isachieved and the bottom product of the column, after being cooled downto normal temperature, is a fully satisfactory coating resin of theetherified amino type. The dehydration step can be operatedsatisfactorily by the combination of the expansion of the reactionmixture, superheated under pressure according to the method of thisinvention, with the feature of blowing alcohol vapor into the bottom ofa column of suitable design, i.e. with as little as possible hold-up.Steam may be used for blowin g the reaction product.

The amount of water formed during the etherification reaction is not sogreat that the removal thereof is essential, and, if desired, this watercan be allowed to remain along with the etherified product. This wateris, in amount, relatively small as compared with the water introducedwith the aqueous formaldehyde used in the first step to provide themelt, and whereas the amount of water introduced with the aqueousformaldehyde is such as to require removal, as indicated, the amountformed during etherification is not so great and its removal is notessential, though it will in many cases be desirable.

For the azeotropic distillation, water-insoluble entraining agents suchas benzene, toluene, or a gasoline cut can be used, so that a ternaryazeotrope is formed from which an aqueous layer separates.

The following examples illustrate the mode of operation of the improvedmethod and indicate some of the variations possible in its application.The reference numbers used in the examples refer to the drawing, whereina flow sheet for the process is set forth. The examples indicate theproportions of alcohol used. In general, known proportions for this stepcan be used.

Example 1 In accordance with the drawing, urea was fed by a continuousconveyor balance 1 at a rate of 6.0 kg. per hour into an elongateddissolving mixer 2 where it was dissolved in a stream of 20.2 kg. perhour of 37% commercial aqueous formaldehyde solution whose pH wasadjusted to 9 by adding small quantities of sodium hydroxide solution.These rates of feed correspond to a molar ratio of urea to formaldehydeof 1 to 2.5. The solution was heated to a temperature between and 92 C.and allowed to react for 20 minutes in the reaction coil 3. The hotsolution of dimethylolurea formed in the reaction coil 3 was admittedthrough the valve 4 into the thin layer evaporator 5 which was operatedwith a steam jacket temperature of 120 C. at an absolute pressure of 35millimeters mercury column. The water distilled from the evaporator 5was condensed in the condenser 6 and showed a formaldehyde contentbetween 1 and 2%, which corresponds to a loss between 1.5% and 3% of theformaldehyde feed. The fused dehydrated reaction product contained onlyabout 3% of water and was withdrawn from the evaporator by a transferpump 7, at a temperature of 95 C. and fed directly into the reactorsystem constituted by a flow path through the agitator 10 and thereaction coil 11, both operated at a pressure of 7 atmospheres gauge.The dimensions of the lines from the evaporator 5 through transfer pump7 to the mixer agitator 10 were such that the transfer time for the meltwas only about 30 seconds.

Butanol was acidified to an acid value of 4 using 0.85 grams ofphosphoric acid per kilogram butanol and per unit acid value. Thisacidified butanol was fed by pump 8 at a rate of 17.4 kg./ h.corresponding to a ratio of 2.4 moles butanol per 1 mol urea through thepreheater 9 into the elongated agitator 10. The time of residence in theagitator was 8 minutes. When the preheating temperature of the butanolwas adjusted to C., the mixture in the agitator assumed a temperature ofC. At this temperature the reaction in the agitator proceededsufiiciently far so that a homogeneous solution entered the reactioncoil 11. In the first part of the reaction coil 11, this solution washeated to 155 C. and allowed to react in the reaction coil 11 for atotal time of 15 minutes. The reacted mixture which still had atemperature of C. was expanded through the expansion valve 12 into thecolumn 13, operated at atmospheric pressure. The pressure in agitator 10and the reaction coil 11 up to the expansion valve 12, was 7 atmospheresgauge.

Utilization of a reaction coil such as reaction coil 11 for theetherification and condensation reaction is preferred, and whenutilizing such means for the reaction,

it is preferred that the reaction be carried out at conditions otherthan reflux. Thus, it is preferred that the temperature be below theboiling point for the pressure utilized. Refluxing conditions inequipment such as the reaction coil have the disadvantage that curing ofthe resin occurs on the wall of the coil, and this interferes with heattransfer and eventually clogs the equipment.

Butanol vapor was generated in evaporator 14 and introduced into thelower part of column 13 at a rate of 8.1 kg./h. which was 216% of thequantity needed theoretically in order to form the azeotropie mixturewith all the Water present. Heat was applied to the reboiler 15 to sucha degree that the content of free solvent butanol in the product wasreduced to about 30% The product withdrawn from the bottom of the columnwas cooled in cooler 16. It had a viscosity of 11,000 cp. at 20 C. and asolids content of 70%. It had a white spirit tolerance of 2.4 grams per1 gram of product and a very good compatibility with alkyds and epoxyresins. Paints made with this resin had exceptionally rapid curingproperties and the cured paint film was very hard and had very goodgloss and gloss retention. The paints were stable on storage for morethan double as long as those based on a resin with identical compositionproduced by batch reaction with a reaction time of 6 hours for the firstplus 10 hours for the second stage.

Example 2 The same apparatus was used as in Example 1 and the rates offiow were identical to those applied in Example 1. The only differencein the operating conditions were, that the butanol was acidified to anacid value of 11.0 by adding per liter of butanol 0.36 gram ofphosphoric acid and 1.61 grams of phthalic anhydride for every unit ofacid value and that steam with a pressure of 10 atmospheres gauge wasused in the preheater 9 so that the acidified butanol entered theagitator 10 with a temperature between 175 and 180 C. in the liquidstate. Thereby the reaction temperature in the well insulated reactorsystem consisting of the agitator 10 and the coil 11, was kept so highthat the reacted mixture immediately before the expansion valve 12 stillshowed a temperature of 150 C. The resin produced in Example 2 showedproperties which were very similar to those of the product of Example 1.

Examples 3-11 Examples 3 to 11 were carried out using the same apparatusunder reaction conditions shown in Table I. For ease of comparison theconditions of Examples 1 and 2 are also listed in Table I. In Examples7, 8 and 11 the steam pressure in the reboiler 14 was adjusted to 3.5atm. gauge corresponding to a condensation temperature of 147 C.Moderate vacuum was applied to column 13, so that the solids content atthe bottom of the column rose to 60%. In Examples 7, 8, and 9 thedimensions of the transfer line were reduced from that applied inExample 1, so that the transfer time from the evaporator 5 to theagitator was only seconds. In Examples 7 and 8, 35% of the n-butanolused was not acidified and was passed into the transfer line immediatelybefore the transfer pump 7. This procedure was followed in order toreduce tendency of incrustation and fouling of the transfer pump 7. InTable I, PA (in reference to the catalyst) means phthalic acid.

The resins from all the examples, with the exception of No. 9, hadexceptionally high white spirit tolerance. The compatibility with alkydswas excellent for the product of all examples without exception. Thegloss of paint films made from the various resins was highest for theproducts of Examples 1, 4, 5 and 7 and was equal to films made with thebest competition resins on the market. The pigment wetting propertieswere best for the products of Examples 1, 5 and 7.

The oven curing properties of the resins produced in Examples 3, 4, 6, 7and 9 are shown in Table II in comparison with two well known commercialfast curing resins, (A) based on urea, and (B) based an melamine. A ballpendulum hardness tester was used.

All resins were tested in combination with one and the same commercialalkyd resin based on 41% phthalic anhydride and 39% of a mixture ofcoconut oil and dehydrated castor oil. This alkyd had an acid value of10 and its solution in 50% xylene had a viscosity of 3000 op. at 20 C.

The etherified urea and thiourea formaldehyde resins 3, 4, 6, 9, A and Cwere combined in the weight ratio 40% amino formaldehyde resin to 60%alkyd resin while the etherified melamine formaldehyde resins 7 and Bwere combined in the ratio 25% amino resin to 75% alkyd.

In all tests the film thickness was 20 and the curing temperature 120 C.

In order to verify the superior oven curing properties of the resinsproduced according to the present invention, the products of Examples 1and 7 were compared with corresponding resins of strictly identicalcomposition (i.e. the proportion of urea nitrogen, combinedformaldehyde, and combined alcohol determined by analysis of each of theresins was the same) made by the conventional batch reaction method.Thus, a reaction time of 6 hours was applied for the first stage and 10hours for the second stage when producing the butylated urea resin D.The melamine resin E was produced by the conventional method which takes10 hours for the first reaction stage, i.e. reaction of formaldehydewith melamine in presence of butanol and removal of bulk of waterintroduced with the formaldehyde, and 12 hours for the second reactionstage, i.e. etherification, condensation and removal of the water ofreaction. The results of the comparison are shown in Table III. The samealkyd as described in connection with Table II was used for preparingthe paints. The curing temperature was 120 C. and the ratio of butylatedurea formaldehyde resins to alkyd used was the same as for theexperiments of Table II.

However, a ratio of only 20% butylated melamine formaldehyde resin to ofthe standard alkyd described was chosen in order to prepare softer paintfilms which facilitate the measurements and the evaluation of resultswith these relatively hard resins. For the same reason and in order todemonstrate the feasibility of low curing temperatures for the new typesof resin, the paint films based on melamine were stoved at only C. Thehardness was determined with a Sward Rocker.

The results shown in Tables II and III show that the aminoformaldehyderesins etherified according to this invention and under superatmosphericpressure and at temperatures exceeding the boiling point of the mixtureat atmospheric pressure, require considerably shorter times for curingthan similar resins produced at lower temperature and atmosphericpressure (Example 3) or than conventional commercial fast curing resins.However, the product of Example 3 shows that even if temperatures belowthe boiling point of the mixture are used, the resins made according tothe present invention show relatively fast curing properties in linewith the best commercial resins on the market. This result is due to thefeature of letting the practically anhydrous fused methylol compoundreact with the acidified alcohol during a relatively short time ofreaction.

When a similar resin was prepared using the same proportions of rawmaterial as those used in Example 3, but applying conventional batchoperating methods with a corresponding long time of reaction, the resinC in Table II was obtained. This resin is obviously not fast curing, butis a satisfactory conventional type.

All urea resins from Examples 1-6 inclusive and Examples 10 and 11, weresubjected to cold curing tests in presence of an acid catalyst and asuitable alkyd plasticizer. They all showed excellent cold curingproperties. Nevertheless, the prepared application mixtures had five toten times longer pot lives than those prepared from commercial referenceresins with equally fast cure.

Molar ratio N-compJalcohoL TABLE I Example 1 2 3 4 5 6 7 8 9 10 11N-Oompound:

Type 1 Urea Urea Ure Urea Urea Urea Melam. Melam. Thiour. Urea Urea kgJ6.0 6.0 6.0 6.0 6.0 6. 6.0 6.0 6.0 6 0 6. 0 37% Formaldehyde:

H 9.0 9.0 9.0 9.0 9.0 9.0 8.5 9.0 9.0 9.0 9.0 kg./h 20.2 20. 2 20. 217.8 17.8 20.2 17. 4 17. 4 16.0 16. 2 20. 2 Molart ratioN-compJformaldchyde 1/2. 1/2. 5 1/2. 5 1/2. 2 1/2. 2 1/2. 5 1/4v 5 1/4.5 1/ 5 1/2. 0 1/2. 5 Bean ion:

C 90 90 90 90 90 90 95 95 90 90 90 Min 25 25 25 25 25 25 5 5 25 25 25Evaporator:

Jacket, C 120 120 120 120 120 130 145 145 120 120 120 Vacuum, mm. Hg 3535 35 35 35 35 760 760 35 35 35 Melt, temp. C 95 95 95 95 100 100 105105 95 100 95 Transfer time:

Secs 30 30 30 30 30 30 15 15 30 15 30 Type 2 n-But. n-But. n-But. n-But.n-But. s-But. n-But. n-But. n-But. Isob. n-Pen. kg./h 17.40 11.8 8. 514. 8 12. 5 14. 8 26. 5 10. 2 8. 5 14. 8 17. 8 Alcohol:

Acid value 4. 0 11.0 12.0 8. 8 4. 0 5. 7 0.5 1.0 7. 5 11.0 11.0 CatalystPA 4 Mixer, C 85 120 85 15 85 Reaction coil:

C 150 150 85 150 135 110 120 150 150 150 110 15 30 10 15 7 30 30 30Pressure, kgJcmfi 7 7 0 7 7 5 3 7 7 7 7 Alcohol vapor:

kg./h 8.1 8.1 12.6 7. 4 9. 6 9.6 8.1 8.1 8.1 7. 4 9. 6 Percent of theor216 216 352 198 297 250 211 195 292 198 248 I Melam.=melamine;Thiour.=thiourea. 3 HaPOi. n-But.=n-but-anol; s-But.=sec.-butanol;Isob.=isobutanol; n-Pen.= 4 PA+H PO4. n-pentanol. 5 Formic acid.

TABLE II 30 temperature in reactor 10 reached 110 C. and the tem- Paintfilm prepared with butylated amino resins (25%) perature in the reactioncoil 11 averaged 150 C. The

in combination with a standard alkyd resin (75%). Film etherified andcondensed resin solution prepared and dethickness; 20 hydrated byazeotropic distillation in column 13 as described in Example 1 andWithdrawn through the cooler PendulumHardness 16 contained 56.9% solidsby evaporation and had a Pmduct Tested 15 min 30 min. 60 mm viscosity of670 cp. at 20 C. When it was used to prepare 9 a coating composition inthe same manner as shown in a? g? g? Table II the pendulum hardness of a20p. film measur 23 s 2% after different curing times at 120 C. was: 485s 5s 27 48 56 Curing tlme (IIllIL). Hardness 33 41 46 20 29 41A=Commercial fast curing American butylated urea formaldehyde resin(Beetle 220-8).

B=Comn1ercial fast curing American melamine formaldehyde resin Fcomparison h same molal ratio of urea to (Uformite MM 55). a

C=Conventional commerical butylated urea formaldehyde resin proaqueoushy e s reacted in the conventional ducod with same proportions of rawmaterials as used in Example 3. b t h method and the heating of theaqueous reaction mixture was continued until a sample of it onevaporation to the same Water content of 3.5% left a syrupy residue 50:ith no tendency to crystallize. It was then dehydrated by vacuumevaporation at a temperature not exceeding 60 C. to said water contentof 3.5% and the syrupy mass TABLE III Comparison of 20 paint filmsprepared from the products of Examples 1 and 7, with paint filmsprepared from conventionally produced resins of identical composition.

swam Rock Hardness etherified with n-butanol in the conventional batchmanner at a pH adjusted to 5.5 by addition of phosgs g g g gj gt f i mg15 3O 60 phoric acid. The product was freed from the Water of Curingtemperature, 120 120 120 reaction by the conventional azeotropic batchdistillagfi i: g; tion. The resulting resin solution in n-butanolcontained (1)) Mela a solids as determined by evaporation. When it wasaigiif i C 93 33 3g used to prepare a coating composition in exactly theE 1 15 16 0 same manner and using the same proportions of ingredients asspecified in Table 2 the pendulum hardness of a 207/. film measuredafter the specified curing times Example 12 at 120 C. was:

The same apparatus and the same conditions of operation were applied asfor Example 1. The rate of feed of Cunng tune (mm-)i Hardness urea was6.0 kg. per hour the rate of feed of 37% aqueous 15 Tacky formaldehyde,however, was 24.4 kg. per hour. These 30 11 rates of feed correspondedto a molal ratio of urea to 60 fofmalfkilyde of 1 to All othercondltlons were the These results when compared with those quoted abovefor Same as In Exalgnple Thus the melt Was Pumped froffl the resinsolution obtained in accordance with the present evaporator 5 Wlth atemperature 0f Its analysls invention clearly show the outstandingadvantage of the showed 3 Of Water- When a Sample of the melt Was methodof the present invention, even if unusually high Withdrawn it tur fid 1a microorystalline paste at room quantities of formaldehyde are reactedwith the urea. temperature and eventually became hard. The melt was Theresults obtained are not caused by disappearance of etherified withn-butanol as described in Example 1. The formaldehyde during theprocedure in accordance with this invention. Analysis showed that afterevaporation of the water from the product of reaction by the method ofthis invention the molar ratio of urea to formaldehyde present in theproduct still was 1 to 2.94. Thus, practically no formaldehyde had beenlost.

Example 13 The apparatus shown in the drawing was changed as follows:The reaction coil 3 was taken away and the reaction coil 11 was replacedby a small high speed mixer consisting of a centrifugal pump which avolume of about 200 milliliters provided with a side-intake into which acaustic soda solution could be injected at a constant, accuratelyadjusted rate in order to neutralize the acid catalyst in the mainstream of the reaction mixture passing through the high speed mixer.These simple arrangements are not shown in the drawing.

Melamine at a rate of 4.42. kg. per hour was fed by the conveyor balance1 into the reactor 2 where it was dissolved in a stream of 14.2 kg. perhour of 37% aqueous formaldehyde whose pH was adjusted to 8.3 byaddition of small amounts of concentrated caustic soda lye. These ratesof feed correspond to a molar ratio of melamine to formaldehyde of 1 to5.0. The solution was heated in the reactor 2 to 95 C., the time ofreaction being 10 minutes. The hot solution was admitted to the thinlayer evaporator 5 which was operated at atmospheric pressure and with ajacket temperature of 145 C. The water evaporated was condensed incondenser 6 and showed a formaldehyde content of 4% by weight. The meltpumped from the evaporator 5 by pump 7 at a transfer temperature of 110C. contained 7% of water and was fed immediately into reactor 10. Thetransfer time was 15 seconds. Methanol was acidified with phosphoricacid to an acid value of 4 as defined in Example 1 and fed by pump 8 tothe heater 9 where it was heated to 60 C. and passed into reactor 10. Inreactor 10 the methanol was allowed to react with the melt with rapidagitation during 3 minutes. The reacting mixture assumed in the reactora temperature of 85 C. and was passed on into the high speed mixerdescribed above where it was neutralized continuously with sodiumhydroxide to a pH of 7. For this purpose a 5-normal sodium hydroxidesolution was injected into the high speed mixer at a constant,accurately adjusted rate governed by the pH value. This rate was about330 ml. per hour. The neutralized solution was expanded through valve 12into column 13 where part of the methanol and of the water present wasevaporated so that the concentrate leaving the bottom of the column hada solids content of 70%. It was withdrawn through the cooler 16. Itshowed a viscosity of 274 cp. and could be diluted with 6 volumes ofwater without precipitation. Water-soluble stove curing coatingcompositions were prepared from this product by combination withwater-soluble alkyd resins.

Example 14 The apparatus used was the same as used in Example 13. Theconditions of operation and the rate of feed of the melamine were thesame as in Example 13. The rate of feed of 37% aqueous formaldehyde,however, was increased to a ratio of 7 mols of formaldehyde to 1 mol ofmelamine. The amount of phosphoric acid added to the methanol wasincreased so that the methanol had an acid value of 5.0. In column 13the water was removed from the accurately neutralized reaction mixturewith the aid of vapors of xylene introduced through the evaporator 14.The heat supply in the reboiler 15 was adjusted so that the dehydratedxylene solution of the methylated melamine-formaldehyde resin formedcontained 70% of solids.

Example 15 The apparatus was the same as that described in Example 13with the exception that column 13 and its accessories 14 and 15 wereremoved and replaced by a thin layer evaporator whose vapor outlet wasconnected with condensor 17 and whose bottom outlet was connected withcooler 16.

The same rates of feed of melamine, formaldehyde, methanol andphosphoric acid catalyst were used as in Example 14 and the sametemperatures as in Example 13. The reacted mixture was neutralizedaccurately in the high speed mixer and admitted to the thin layerevaporator where all the water was removed together with the excess ofmethanol. The product was withdrawn as a melt at a temperature of 120 C.from the bottom of the thin layer evaporator and cooled in the cooler 16to 60 C. When it was allowed to cool down to room temperature itsolidified to a paste which was soluble both in water and in whitespirit. It contained less than 1% of water and upon analysis it showed acomposition indicating hexamethoxmethyl-melamine. When this product wasused in making coating compositions these gave films which becameextremely tough and hard upon curing.

What is claimed is:

1. Process for the production of etherified amino-formaldehyde resinWhich comprises contacting formaldehyde and an amino compound containingthe group in which X is a member selected from the group consist ing ofO, S, and N(l} in an aqueous medium to condense the formaldehyde andamino compound and form a condensation product in aqueous solution,rapidly heating said aqueous solution for a time not in excess of 60seconds to expel water therefrom and provide a substantially unstable,anhydrous melt of the condensation product which is soluble in waterwith unlimited dilution, contacting said condensation product in theform of unstable, anhydrous melt with alcohol in liquid form andselected from the group consisting of primary and secondary monohydricand polhydric aliphatic alcohols, and an acid catalyst at a temperatureabove about C. for a residence time of less than 1 hour sufficient foretherification of the condensation product with the alcohol to form saidetherified amino formaldehyde resin.

2. Process according to claim 1, wherein the amino compound is selectedfrom the group consisting of urea, thiourea, and melamine.

3. Process according to claim 1 wherein said heating to expel water isat a temperature in excess of about C.

4. Process according to claim 3 wherein said substantially anhydrousmelt is formed in an evaporating zone, and is withdrawn from theevaporating Zone as a melt and is initially contacted with said alcoholwithin 2 minutes following said withdrawal.

5. Process according to claim 1, wherein the amino compound is selectedfrom the group consisting of urea, thiourea, and melamine, wherein thealcohol is a primary alcohol having 4-5 carbon atoms, wherein thetemperature of said contacting of condensation product and alcohol isabout -170" C., the pressure superatmospheric, and the residence time isless than about 30 minutes.

6; Process according to claim 1, wherein said substantially anhydrousmelt is formed in an evaporating zone, the anhydrous melt is removedfrom the evaporating zone immediately following its formation and isinitially contacted with said alcohol Within 2 minutes following saidremoval.

7. Process according to claim 1, wherein the alcohol is a primaryaliphatic alcohol having up to about 8 carbon atoms.

8. Process according to claim 1, wherein the alcohol is a primaryaliphatic alcohol having 4-5 carbon atoms.

9. Process according to claim 1, wherein the temperature of contactingof said melt and said alcohol is about 100-175 C. and the pressure issuperatmospheric.

10. Process according to claim 1, wherein the residence time is lessthan about 30 minutes.

11. Process according to claim 1, wherein said substantially anhydrousmelt is formed in an evaporating zone, the anhydrous melt is removedfrom the evaporating zone immediately following its formation and isinitially contacted with said alcohol within 2 minutes following saidremoval, wherein the amino compound is selected from the groupconsisting of urea, thiourea, and melamine, wherein the alcohol is aprimary aliphatic alcohol having 4-5 carbon atoms, wherein thetemperature of contacting of said melt and said alcohol is about 100470C., the pressure is superatmospheric, and wherein said residence time isless than about 30 minutes.

12. Process according to claim 1, the product of said contacting saidcondensation product and alcohol being a mixture comprising theetherified amino compound, water, and unreacted alcohol, said processcomprising heating the mixture to evaporate water therefrom as anazeotropic mixture of said alcohol and water.

13. Process according to claim 1, wherein the product of said contactingof condensation product and alcohol is blown with steam.

14. Process according to claim 1, wherein the product of the contactingof condensation product and alcohol comprises a mixture of saidetherified amino compound and water, and said mixture is contacted withaliphatic alcohol vapor for azeotropic distillation of water therefrom.

References Cited UNITED STATES PATENTS 2,322,979 6/1943 Siegel 2602,377,422 6/1945 Hodgins et al. 26070 2,537,131 1/1951 Grossman 260249.62,849,421 8/1958 Weldin 26070 FOREIGN PATENTS 557,364 11/1943 GreatBritain; 724,972 2/1955 Great Britain.

WILLIAM H. SHORT, Primary Examiner.

H. SCHAIN, Assistant Examiner.

Patent No. 3,392,150

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION July 9, 1968Herbert P. A. Groll It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected asshown below:

Columns 11 and 12, TABLE I twelfth column, line 13 thereof, "17.8"should read 17.6 same table, nineth column, line 16 thereof, "1/1.60should read 1/4.60

Signed and sealed this 23rd day of December 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

